Objective: To investigate the effects and possible mechanisms of caffeic acid phenethyl ester (CAPE) on the replication, amplification, and fibre formation of prions (PrPSc). Methods: The CCK8 assay was used to detect the cell viability of the prion-infected cell model SMB-S15 after CAPE treatment for 3 days and 7 days and the maximum safe concentration of CAPE for SMB-S15 was obtained. The cells were treated with a concentration within a safe range, and the content of PrPSc in the cells before and after CAPE treatment was analyzed by western blot. Protein misfolding cycle amplification (PMCA) and western blot were used to assess changes in PrPSc level in amplification products following CAPE treatment. Real-time-quaking induced conversion assay (RT-QuIC) technology was employed to explore the changes in fibril formation before and after CAPE treatment. The binding affinity between CAPE and murine recombinant full-length prion protein was determined using a molecular interaction assay. Results: CCK8 cell viability assay results demonstrated that treatment with 1 μmol/L CAPE for 3 and 7 days did not exhibit statistically significant differences in cell viability compared to the control group (all P<0.05). However, when the concentration of CAPE exceeded 1 μmol/L, a significant reduction in cell viability was observed in cells treated with CAPE for 3 and 7 days, compared to the control group (all P<0.05). Thus, 1 μmol/L was determined as the maximum safe concentration of CAPE treatment for SMB-S15 cells. The western blot results revealed that treatment with CAPE for both 3 and 7 days led to a detectable reduction in the levels of PrPSc in SMB-S15 cells (all P<0.05). The products of PMCA experiments were assessed using western blot. The findings revealed a significant decrease in the levels of PrPSc (relative grey value) in the PMCA amplification products of adapted-strains SMB-S15, 139A, and ME7 following treatment with CAPE, as compared to the control group (all P<0.05). The RT-QuIC experimental results demonstrated a reduction in fibril formation (as indicated by ThT peak values) in CAPE-treated mouse-adapted strains 139A, ME7, and SMB-S15, as well as in SMB-S15 cells infected with prions. Furthermore, CAPE exhibited varying degrees of inhibition towards different seed fibrils formation, with statistically significant differences observed (all P<0.05). Notably, CAPE exhibited a more pronounced inhibitory effect on ME7 seed fibrils. Molecular interaction analyses demonstrated significant binding between CAPE and murine recombinant prion protein, and the association constant was (2.92±0.41)×10-6 mol/L. Conclusions: CAPE inhibits PrPSc replication, amplification, and fibril formation in vitro possibly due to specific interactions with the prion protein at the molecular level.
目的： 探究咖啡酸苯乙酯（CAPE）对朊病毒（PrPSc）复制、扩增及纤维形成的影响及可能的机制。 方法： 通过CCK8实验检测CAPE处理3、7 d后朊病毒感染细胞模型SMB-S15的细胞活力，得出CAPE对SMB-S15的最大安全浓度；选取安全范围内的浓度处理细胞，利用蛋白质免疫印迹方法分析CAPE处理前后细胞内PrPSc的含量变化。利用蛋白质错误折叠循环扩增（PMCA）技术和蛋白质免疫印迹方法检测CAPE处理前后扩增产物中PrPSc的含量变化。利用实时震动蛋白诱导扩增（RT-QuIC）技术检测CAPE处理前后朊蛋白纤维形成的变化情况。通过分子相互作用检测CAPE与小鼠重组全长朊蛋白的结合能力。 结果： CCK8细胞活力实验结果显示：1 μmol/L CAPE处理细胞3、7 d时细胞存活率与对照组相比，差异无统计学意义（均P>0.05），当CAPE浓度超过1 μmol/L时，CAPE处理细胞3、7 d细胞存活率降低，与对照组之间差异均存在统计学意义（均P<0.05），因此1 μmol/L为CAPE处理SMB-S15细胞的最大安全浓度。蛋白质免疫印迹实验结果显示：CAPE处理3、7 d均可检测到SMB-S15细胞中PrPSc含量的降低（均P<0.05）。PMCA实验产物通过蛋白质免疫印迹方法检测结果显示：经CAPE处理后，适应株SMB-S15、139A、ME7的PMCA扩增产物中PrPSc含量（相对灰度值）降低，与对照组相比差异有统计学意义（均P<0.05）。RT-QuIC实验结果显示：CAPE处理后139A、ME7、SMB-S15小鼠适应株和朊病毒感染细胞SMB-S15在反应中形成朊蛋白纤维（ThT峰值）均降低，且CAPE对不同种子朊蛋白纤维的抑制程度差异有统计学意义（均P<0.05），其中对ME7的抑制作用更明显。分子相互作用结果显示：CAPE与鼠源重组朊蛋白存在明显的分子结合，平衡解离常数KD为（2.92±0.41）×10-6 mol/L。 结论： CAPE对PrPSc体外复制、扩增和纤维形成均具有抑制作用，可能与CAPE和朊蛋白特异性结合有关。.